DESCRIPTION: This is an amended KO1 application requesting five years of support to provide research training by using an SIV macaque animal model to study the role of the BBB in the development of encephalitis and AIDS dementia. The candidate's preliminary data have demonstrated that neurovirulent but not non-neurovirulent strains of SIV productively infect brain microvessel EC both in vivo and in vitro. This result suggests that the neuroendothelial cells may play an important role in the pathogenesis of SIV encephalitis, and that compromise of CNS EC function may play a pivotal role in BBB disturbances. Furthermore, infection of EC, and alterations in the EC expression of cell adhesion molecules (CAMs) may also contribute to a loss of BBB integrity. The central hypothesis of this application is that BBB dysfunction plays a crucial role in the development of encephalitis and AIDS-related dementia. The first Specific Aim of this application is to assess BBB integrity during acute, latent, and chronic stages of SIV infection to determine whether loss of BBB function is associated with CNS viral load, and CNS pathology. The second Specific Aim is to examine the dynamics of EC infection during disease progression in order to determine if EC infection is associated with altered BBB integrity, increased CNS viral load, and CNS pathology. For both Aims 1 and 2, in vivo analysis employing immunohistochemistry, in situ hybridization, and reverse transcriptase polymerase chain reaction (RT-PCR) done in situ, will be performed on CNS tissues from animals at various stages of disease. CNS microvessel isolation will permit further characterization of BBB integrity and EC infectivity. The third Specific Aim is to determine if CAMs mediate the interaction between EC and infected and uninfected peripheral blood lymphocytes and monocyte/macrophages during disease progression. Adhesion will be examined both in vivo and in vitro to define the functional role of CAMs during disease progression. Overall, these studies are intended to contribute to the understanding of the role the BBB plays in the development of lentiviral encephalitis.